The purpose of your diaphragm is to use suction produced by your venturi (that's placed in the main throat of your air intake in your inlet manifold) to pull your rack towards the "low fuel" position.
So the hose from the vacuum side sucks on the diaphragm (remembering that the hoses cross over each other on early B-engines like mine) towards the fuel shut-off position (whilst the other side of the diaphragm is simply exposed to the "post-air-filter-pressure" via the other hose).
In other words, the "natural position" of your rack (when it is not being exposed to engine-vacuum) is one where it would supply enough fuel for starting a warm engine and too-much fuel for a normal 650rpm idle.
So what I'm leading to here is that leaks on the diaphragm housing wouldn't usually stop an engine from starting. Instead they'd usually still allow it to start but cause it to idle too fast.
Now you say "will not run". Does that mean it starts OK but stalls whenever you take your foot off the accelerator? (More explanation required.)
Anyway ..... Check that your butterfly looks similar to mine (ie. almost completely closed) when your foot is off the accelerator and that it opens fully when your foot is hard down. (I'm thinking that with a dodgy accelerator cable etc perhaps you may have knocked something during your diaphragm exchange that could have altered the way your butterfly operates.)
If that is OK, and your engine still doesn't start and idle nicely (and assuming it could do so before your diaphragm change) - then you must have messed up something with your installation.
If so, you're not the only one to do this..
Here's a thread from Rufus for example:
Replaced pump diaphragm now no power
Perhaps you made the same error as he did?
